My T has her doctorate and I still address her by her first name. But I did ask her first how I should address her.

Technically, you should not address your T as doctor since she does not have a doctorate. It might even be insulting to do so. I had a nurse practitioner as my primary. I called her Dr. once and she was offened. She told me she is not a doctor and to just call het by her first name.

Ex-T also had a doctorate and I referred to her by her first name.